1. Field of the Invention
This invention relates to a method for the production of a halogen-containing aromatic compound useful as a raw material for resins which excel in heat resistance, chemical resistance and water repellency, and have a low dielectric and a low refractivity.
This invention further relates to a novel halogen-containing naphthalene compound useful as a raw material for resins which have a high glass transition temperature and excel in chemical resistance, water repellency, and low refractivity.
2. Description of the Related Art
It has been heretofore known that halogen-containing aromatic compounds, particularly those halogen-containing aromatic compounds which incorporate a difluoroalkyl group or a bromodifluoroalkyl group therein, are useful as raw materials for resins which excel in heat resistance, chemical resistance and water repellency, and have a low dielectric and a low refractivity. Among other halogen-containing aromatic compounds, particularly .alpha.,.alpha.'-dibromo-.alpha.,.alpha.,.alpha.',.alpha.'-tetrafluoro-p-x ylene is known as constituting itself a raw material for per-.alpha.-fluoro[2,2]paracyclophane which is a precursor for poly(.alpha.,.alpha.,.alpha.',.alpha.'-tetrafluoro-p-xylene). For example, Journal of Organic Chemistry, Vol. 62, pp. 7500-7502, 1997 has stated that per-.alpha.-fluoro[2,2]para-cyclophane derived from a halogen-containing aromatic compound can be used as a precursor for poly(.alpha.,.alpha.,.alpha.',.alpha.'-tetrafluoro-p-xylene) (referred to simply as "Parylene F" in the present specification) and that the Parylene F resulting from the polymerization thereof possesses a low dielectric constant and can be used an interlayer insulating film for semiconductors of the next generation. As means for the production of such a halogen-containing aromatic compound, a method which comprises irradiating an aromatic compound incorporating therein a CX.sub.2 H group (wherein X represents F or Cl) with an UV light while using bromine (Br.sub.2) as a brominating agent (Zhurnal Organicheskoi Khimii, 1993, 29, 1999) and a method which comprises effecting the irradiation with light while using N-bromosuccinimide as a brominating agent (Zhurnal Organicheskoi Khimii, 1993, 29, 1999; J. Org. Chem., 1993, 58, 1827-1830) have been known.
The former method which uses bromine (Br.sub.2) as a brominating agent, however, has the problem of obtaining the target compound only in a low yield (27 to 30%). Then, the latter method which uses N-bromosuccinimide as a brominating agent, although indeed enables the relevant reaction to proceed efficiently, it still entails the problem of suffering succinimide to accumulate on the side of light incidence of the reaction vessel made of glass with the progress of the reaction and eventually impede the progress of this reaction and the problem of using N-bromosuccinimide, an expensive raw material, and consequently suffering the target product obtained by such a method to become inevitably expensive. Thus, none of the known methods is capable of producing a halogen-containing aromatic compound inexpensively in a high yield.
The semiconductor technology represents the existing forefront techniques for fine fabrication and mass production. The technology for the production of semiconductors culminates in the technique for fine fabrication and the technique for high density packaging. It has promoted the advance of semiconductors toward higher integration, greater addition to function, higher reliability, and lower cost. The formation in particular of a multilayer wiring which has emerged from the growth of high integration dictates fulfillment of such requirements as ample heat resistance, high electric insulation, low dielectric constant, high chemical and mechanical stability, and easy fine fabrication.
Since the Parylene F excels in insulation and yet possesses only such low thermal stability as 450.degree. C., it fits only limited applications on account of insufficient heat resistance when higher heat resistance is required as, for example, in the process for the production of semiconductors. Various organic high polymers which are aimed at exalting ability of fabrication and facilitating impartation of varying properties have been developed and already adopted for actual use in numerous fields. It is, therefore, proper to conclude that the desirability of developing a resin excelling in heat resistance or a raw material for such a resin is rated very high.